1. Field of the Invention
The invention relates generally to means for measuring the level of liquid in a tank and particularly to a direct reading gauge providing visual access to the gauge element from the exterior of the tank although the apparatus itself is not exposed to the contents of the tank. A true indication of the liquid level is visually signalled by reading a flexible, endless tape loop through a window.
The invention is concerned with the provision of a flexible, endless loop band or tape member having magnetic armature means capable of moving within an outer housing extending into a tank. The interior of the housing is sealed off from the contents of the tank. A float on the outside of the housing carries means for magnetically attracting the magnetic armature means of the gauge element. Tape guide rollers are provided at opposite ends of the interior of the housing and maintain the endless loop under full extension.
2. Description of the Prior Art
It has been well known in the past to use solid, substantially rigid but lightweight rods which are tubular, square or rectangular or, in a copending application assigned to the assignee, a flexible, tape-like gauge member which is made of plastic or other light-weight materials, which can be printed or embossed in a rotary type printing apparatus. Typical stick gauges are disclosed, for example in the patents to H. Nussbaum, U.S. Pat. Nos. 3,407,660 and 3,572,122, assigned to a predecessor in interest of the assignee of the present invention. Of additional interest is the patent to J. H. Field, et al., U.S. Pat. No. 2,949,776, also assigned to the predecessor in interest of the assignee herein.
A common problem to these devices is that they must extend from the tank body when in use. A failure to secure the gauge assembly after use will permit the gauge to extend at inopportune times, thereby increasing the risk of damage or breakage. Moreover, such devices generally require a tool, which may be simply a coin, to release the gauge mechanism so that it can be read.
Another problem common to all "stick-type" gauges which are generally read by a local ground crew is that arising from communication and training. Since aircraft now fly all over the world, some ground crews are better trained and more dependable than others. However, language barriers contribute to the difficulty of obtaining reliable information as to the status of the fuel during any stopover.
Reports of aircraft departing with insufficient fuel on board can not be discounted. Whether this is caused by an inability to read the gauge or an inability to communicate the results is never clear. The dangers to the aircraft are extraordinary. Therefore it is sufficient to say that what is needed is a gauge that can be visually read by any member of the flight crew while making a routine inspection of the aircraft.